Polymer mortar composite pipe material and manufacturing method

ABSTRACT

Composite material and plunger-cast pipe manufacturing method and system wherein the composite material includes waste, chemically unmodified PET material, one or more waste filler materials (e.g. rock crusher fines, lime sludge or waste coal combustion by-products), and fiber reinforcement (e.g. glass, metal, ceramic, carbon, organic, and polymer fibers) and wherein the PET material is melted and mixed in a container to disperse filler material and fiber reinforcement in the PET material. The resulting mixture can be formed into a tubular pipe shape using the plunger-cast manufacturing method and system wherein a plunger piston and inner collapsible mold are pushed into the melted composite material contained in an outer mold. When cooled and solidified in the mold, a composite material having a matrix comprising PET with filler material and fiber reinforcement distributed in the matrix is formed in the shape of a tubular body.

This application is a division of U.S. application Ser. No. 11/029,184filed Jan. 4, 2005 now abandoned, which claims benefit and priority ofU.S. provisional application Ser. No. 60/534,440 filed Jan. 6, 2004.

FIELD OF THE INVENTION

The present invention provides polymer mortar composite materialsincluding recycled, post-consumer waste polyethylene terephthalate (PET)with waste filler materials and fiber reinforcement and methods of theirmanufacture and methods of their use as pipe in the constructionindustry.

BACKGROUND OF THE INVENTION

Diverting solid waste from landfills is increasingly important due tolimited availability of landfill space, rapidly increasing landfillcost, and environmental threats. The U.S. is the largest global producerof PET containers at nearly 70 percent of the supply [reference 1]. Inthe U.S., estimates indicate that annual production of PET containerswill reach more than 2 million tons [reference 2]. The recycling ratefor PET is about 25 percent [reference 3]. Production of the wastefiller materials is about 500 million tons for rock quarry crusherfines, 10 million tons of lime sludge, and 100 million tons forcoal-combustion by-products. Recycling has emerged as the most practicalmethod to deal with these high-volume waste problems.

In addition, the U.S. has about 19,782 sewerage systems serving about170 million people or about 75 percent of the population [reference 4].As with much infrastructure in this country, this subterranean componenthas also deteriorated due to normal aging, sulfuric acid degradation,under design, poor initial design, and minimal maintenance. It isestimated that 800,000 miles of sanitary sewer line in the U.S. are inneed of rehabilitation and that we are currently making repairs at therate of 2 percent per year [reference 5]. Sixteen thousand miles ofrehabilitation with an estimated 8 thousand miles of new constructioncreate a need for improved pipe material.

An object of the invention is to provide a polymer mortar composite pipematerial that has several beneficial material properties overconventional Portland cement concrete (PCC) pipe and vitrified extrastrength clay tile including high structural capacity, excellent acidresistance, and low density. Equally important is the fact that thematerial components of the polymer mortar composite formulation consistof recycled plastic and waste filler materials (rock quarry crusherfines, lime sludge or various coal combustion by-products). By usingrecycled, post-consumer waste polyethylene terephthalate (PET) insteadof virgin plastic, which is petroleum derived material; use of asignificant volume of crude oil can be reduced.

Another object of the invention is to provide a plunger-castmanufacturing method and system than can increase recycling throughproduction of polymer mortar composite pipe using the composite materialmixtures described herein.

Still another benefit of the invention derives from production of thepolymer mortar pipe to provide a strong, lightweight, and durable pipeproduct for which there is currently tremendous need.

SUMMARY OF THE INVENTION

The present invention provides a composite material and plunger-castpipe manufacturing method and system wherein the composite materialcomprises waste, chemically unmodified PET material, one or more wastefiller materials (e.g. rock crusher fines, lime sludge or waste coalcombustion by-products), and fiber reinforcement (e.g. glass, metal,ceramic, carbon, organic, and polymer fibers). The PET material ismelted and mixed with the other constituents in a container to dispersethe waste filler material and the reinforcement fibers in the PETmaterial. The resulting mixture can be formed into a tubular pipe shapeusing the plunger-cast manufacturing method and system pursuant to anembodiment of the invention wherein a piston and an inner collapsiblemold thereon are pushed into the melted composite material contained inan outer mold. When cooled and solidified in the mold, a compositematerial having a matrix comprising PET with filler material and fiberreinforcement distributed in the matrix is formed in the shape of atubular body. The plunger-cast pipe manufacturing method and system canbe used with other materials as well and is not limited to the compositematerial described above.

In one embodiment of the invention, the solid waste, chemicallyunmodified PET material, waste filler particles and fiber reinforcementare premixed and placed in a melting container for melting of the PETmaterial while the mixture is mixed or stirred. Alternately, the solidwaste, chemically unmodified PET material can be melted in thecontainer, and pre-heated waste filler particles introduced to themelted PET material with the mixture stirred or mixed. Once thePET/filler mixture is homogenized, the fiber reinforcement isincrementally added to the mixture and stirred or mixed. The mixture ofmelted PET material, waste filler particles and fiber reinforcement canbe molded, extruded or otherwise formed.

The invention envisions use of waste PET material from recycled beveragebottles and other sources. In practice of the invention, the recycledwaste PET material is not chemically modified in any way prior tomelting. The solid recycled waste PET material may be washed in tapwater and shredded or otherwise comminuted prior to melting.

The invention envisions use of different types of one or more wastefiller materials including rock quarry crusher fines, lime sludge and/orcoal-combustion byproducts and/or other waste filler materials withcomparable morphological characteristics.

Various amounts of filler material up to about 70 percent (based onweight of PET) in combination with various amounts of fiberreinforcement up to about 6 percent (based on weight of PET and wastefiller) can be included in the composite material. Preferably, the wastefiller content of the composite material is at least about 50 percentand fiber content preferably from about 1 to about 4 percent.

In another illustrative embodiment of the invention, the melted andmixed composite material (or other flowable material) is formed into atubular pipe using a plunger-cast manufacturing method and system. Inpractice of an illustrative method embodiment of the invention, a pistonplunger, base plate, outer rigid cylinder mold, and inner collapsiblemold are first preheated in an oven to about 270° C. The plunger pistonpreferably is a specially shaped, beveled plunger piston attached to ahydraulic piston. The inner collapsible mold is attached to the plungerpiston. The base plate and outer rigid mold are placed under the pistonand the melted composite material is introduced into the outer rigidmold and base plate. The inner mold includes a transverse dimension,such as diameter, that is smaller than that of the outer mold so as toform a space therebetween when the inner mold is positioned in the outermold. The plunger piston with the inner collapsible mold thereon arehydraulically pushed down into the melted composite material, thusforcing the melted composite material outward into the space between theinner and outer molds to form a tubular pipe shape. After the inner moldis fully positioned or inserted into the outer mold, the plunger pistonis removed leaving the inner collapsible mold in place forming the innerwall of the pipe. During curing of the composite material, the innermold can collapse, thus allowing for thermodynamic shrinkage of thecomposite material. Fiber reinforcement significantly reducesdeleterious shrinkage cracks from forming during the cooling process.Once the pipe has cooled enough to solidify, it is removed from the moldand further cooled at room temperature. The plunger-cast manufacturingmethod and system is then reused to manufacture additional tubular pipesections.

The above objects and advantages of the invention will become morereadily apparent from the following detailed description taken with thefollowing drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, and 1C are photographs of three forms of solid waste,post-consumer recycled PET beverage bottle material.

FIGS. 2A, 2B are photomicrographs of fiber reinforcement with wastefiller material (rock quarry crusher fines designated RCF) and FIG. 2Cis a photomicrograph of the particle distributions of the waste fillermaterial (RCF).

FIG. 3A is a side elevation of the plunger piston. FIG. 3B is a sideelevation of the collapsible inner mold. FIG. 3C is a plan view of theinner mold. FIG. 3D is a perspective view of the piston. FIG. 3E is aschematic perspective view showing the inner collapsible mold. FIG. 3Fis a schematic partial enlarged perspective view of the innercollapsible mold edges overlapped and encircled in FIG. 3E.

FIG. 4A is a schematic elevational view of outer rigid mold. FIG. 4B isa schematic elevational view of the bottom plate on which the outer moldsits. FIG. 4C is a plan view of the bottom plate. FIG. 4D is aperspective view of the outer mold. FIG. 4E is a perspective of thebottom plate.

FIG. 5A is an exploded schematic view of components of the plunger-castmanufacturing system. FIG. 5B is an exploded schematic view of theplunger piston having the inner mold thereon and the outer rigid moldlocated below the assembled plunger piston and inner collapsible mold.

FIG. 6 is a side elevation of the plunger piston connected to hydraulicram

FIG. 7 is a side elevation of the inner collapsible mold attached toplunger piston and base plate with outer mold

FIG. 8 is a perspective view of the plunger-cast mold after the plungerpiston has been extracted

FIG. 9 is a perspective view of the plunger cast composite pipe specimen

FIG. 10 is a perspective view of the ultimate three-edge bearing testsetup.

FIGS. 11A through 11J are graphs of applied load versus strain of theultimate three-edge bearing strength tests.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described first with respect to making acomposite material using solid waste, post-consumer recycled PETmaterial and waster filler materials and discontinuous reinforcementfibers. Next the engineering properties of the composite material willbe described, and finally the plunger-cast manufacturing process andultimate three-edge bearing strength tests for pipe specimens will bepresented, all for purposes of illustration and not limitation.

Post-Consumer Recycled PET

Solid waste, post-consumer recycled PET beverage bottle materials areused as the binder material in the composite material and are availablein three forms: (Type 1) sorted, washed and processed; (Type 2) unsortedand shredded; and (Type 3) partially-sorted, shredded and washed. Flakedor pelletized PET commonly available from plastic recycled facilities isreferred to as “Type 1”. PET collected in the form of waste beveragecontainers that have been shredded without removing the labels or capsand no washing is referred to as “Type 2”. PET collected in the form ofwaste beverage containers that have been shredded after removing some ofthe labels and caps and washing in a water bath is referred to as “Type3”. FIGS. 1A, 1B, and 1C show the three forms Type 1, Type 2, Type 3,respectively, of post-consumer recycled PET beverage bottle materialused in the production of composite material pursuant to an illustrativeembodiment of the invention offered for purposes of illustration and notlimitation.

Waste Filler Materials

Several types of waste filler materials can be used in the compositematerial mixture including: (1) rock quarry crusher fines (RCF); (2)coal-combustion by-products (CCBs); and (3) lime sludge from watertreatment plants (LS). Table 1 summarizes the chemical constituents andphysical properties for all waste filler materials used in examplesdescribed below.

Rock Quarry Crusher Fines

Of the 2-billion tons of aggregate produced per year in the U.S.[reference 6], it is estimated that an additional 25 percent to 30percent is wasted due to crushing and screening operations. Thescreening materials (typically 100 percent passing 9.5 mm sieve and upto about 30 percent passing the 0.075 mm sieve) are often stockpiled orput back into the quarry as fill, resulting in zero or negative value.The rock quarry crusher fines used in the examples below comprisedcrushed quartzite. 100 percent of the particles were smaller than 0.15mm and 74 percent smaller than 0.075 mm. Minerals identified in the rockquarry crusher fines consisted of quartz, kaolinite, and talc.

Lime Sludge

Most drinking water is softened and most commonly lime softening isused, introducing slaked lime to remove hardness as calcium carbonateand magnesium hydroxide. About 10 million tons of lime sludge isgenerated in the U.S. annually, which creates disposal problems. Limesludge has very similar chemical composition as limestone. 100 percentof the lime sludge used in the examples below was smaller than 0.075 mm.The only mineral identified in the lime was calcite.

Coal Combustion By-Products

Coal combustion by-products are produced from burning coal in energyproduction facilities and exist in a wide range of gradations andchemical compositions. About 100 million tons of coal combustionby-products are produced in the U.S. annually [reference 7]. Sixdifferent coal combustion by-products were evaluated in this studyincluding: (1) Prairie Creek fly ash (PFA); (2) Ames fly ash (AFA); (3)Iowa State University (ISU) circulating fluidized bed fly ash (CFBFA);(4) ISU stoker fly ash (SFA); (5) ISU circulating fluidized bed bottomash (CFBBA); (6) ISU stoker bottom ash (SBA); and (6) University ofNorthern Iowa (UNI) fluidized bed combustion residue (FBC).

PFA is produced form burning coal originating from the Powder RiverBasin in Wyoming and is burned in pulverized boilers. All particles aresmaller than 0.85 mm and 93 percent are smaller than 0.075 mm. PFAclassifies as an ASTM C618 class C fly ash. AFA is also produced fromburning Powder River Basin coal in pulverized boilers. About 10 percentby weight of municipal solid waste is also burned with AFA coal. Allparticles are smaller than 0.85 mm and 95 percent are smaller than 0.075mm. This material cannot be classified as ASTM class C fly ash sincemunicipal solid waste is burned with the coal. Minerals identified inthe ash are quartz, anhydrite, brownmillerite, lime, periclase, andtricalcium aluminate.

CFBFA and SFA were both supplied by ISU Power Plant, which burns amixture of coal from Illinois and Kentucky. The same mixture of coal isburned in two different types of boilers. The ashes receive their namesfrom the boilers in which they are produced, circulating fluidized bedand stoker boilers, respectively. SFA has the highest loss on ignition(LOI) at 42.4 percent due to inefficient combustion. All CFBFA particlesare smaller than 0.25 mm and 89 percent are smaller than 0.075 mm. Allparticles in SFA are smaller than 2.00 mm and 93 percent are smallerthan 0.075 mm. Minerals identified in the CFBFA are quartz, anhydrite,lime, hematite, and illite. Minerals identified in the SFA are quartz,mullite, hematite, and albite.

CFBBA material has particles with 99 percent smaller than 4.75 mm andonly 1 percent smaller than 0.075 mm. Quartz, anhydrite, lime, hematite,calcite, and portlandite are the minerals identified in the CFBBA.

Due to large particle sizes, SBA was first crushed so that all particlesare smaller than 2.0 mm and 28 percent are smaller than 0.075 mm.Quartz, mullite, Magnetite, and hematite are the minerals identified inthe SBA.

FBC was supplied by the UNI Power Plant, which burns a mixture of coalfrom Kentucky and West Virginia. A pyropower boiler is used to burn thecoal at this location. All particles are smaller than 2.0 mm and 64percent are smaller than 0.075 mm. Minerals identified in the FBC arelime, anhydrite, quartz, and hematite.

Fiber Reinforcement

Fiber reinforcement is added to the composite material to improve itsengineering properties and control thermodynamic shrinkage. Fiberreinforcement can include one or more of glass, metal, ceramic, carbon,organic, and polymer fibers. For the examples described below,discontinuous fiberglass fibers of different lengths (6 mm and 13 mm)were used. The fibers were both chopped strand 919-4 CT fiberglassfibers produced by Vetrotex America, Inc. (Product Nos. CA4J919022 andCA4J919053, respectively). Fiber reinforcement is an essential componentof the composite material for production of the plunger-cast tubularpipe specimens, as without fibers, thermodynamic shrinkage cracksdevelop during the cooling process. Further, the fiber reinforcementenhances uniform distribution of air voids.

Manufacturing Process for Composite Material

Manufacturing of the composite material is initialed by weighting outthe desired post-consumer PET material (Type 1, 2 or 3), the wastefiller material, and fiber reinforcement. The post-consumer PET isintroduced into an electric melting pot and then pre-heated waste fillermaterial is added and mixed with the melted PET. The post-consumer PET,which is a thermoplastic, melts at about 270° C. The filler material canalternately be added to the melted PET prior to heating. A mechanicalstirring device (steel rod or spatula) is used to mix the PET and wastefiller materials. Once mixed, the fiber reinforcement is incrementallyadded and mixed until evenly dispersed in the mixture.

Specimens for engineering property evaluation are prepared bytransferring the composite mixture into preheated mold of the desiredgeometry and allowing the mixture to cool at room temperature.

Engineering Properties of Composite Material Mixtures

Table 2 summarizes engineering properties including density, compressivestrength, tensile strength, and elastic modulus of the compositemixture. Statistical analyses show that the compressive strength,tensile strength and elastic modulus increase with increased fillercontent and fiber content.

Compressive Strength

ASTM C 39/C 39M-99 Standard Test Method for Compressive Strength ofCylindrical Concrete Specimens [reference 8] was used as a guide to testthe compressive strength for the composite cylinder specimens. ASoiltest machine was used to produce the compressive force. The smallestdivision on the testing machine was 0.2 kN. Loading rate was calculatedby measuring the elapsed time for increment 2 kN. The load of 2 kN wasthen divided by the initial cross-sectional area to determine thecompressive strength. Compressive strength was then divided by theelapsed time in seconds to determine the loading rate.

Test specimens were constructed from different composite mixtures. Twocylinder specimens from every composite design mix were tested. Testspecimens had a diameter of about 50.8 mm and a length of 101.6 mm. Loadrate was continuous and without shock and within the range of 0.15 to0.35 MPa/s. The diameter of the cylinder specimens was determined byaveraging two diameters in the middle of the specimen at right anglesfrom each other. Lengths of the cylinder specimens were determined byaveraging two lengths.

Cylinder specimens were positioned by centering them vertically on oneof their ends in the middle of the bearing block. The ram was thenlowered so that it came into contact with the top end of the cylinderspecimen. The testing machine was set to controlled test, which startedthe loading. Loading continued until the load indicator decreasedsignificantly. This decrease indicated that the cylinder specimenfailed. The maximum load was then recorded to the nearest 0.2 kNdivision. The testing machine was then unloaded and the sample removed.This process continued until all of the cylinder specimens were tested.

Results indicate that the average compressive strength for 96 specimensis 38.8 MPa, which is slightly greater than the ordinary PCC strength of15 to 35 MPa. Elastic modulus varied from 1300 MPa to 5700 MPa. Theaverage elastic modulus was 3300 MPa (24 specimens), which is 7 to 10times lower than ordinary PCC. Density of the composite ranged from 1.2to 1.8 g/cm³ with an average of 1.6 g/cm³, which is lower than ordinaryPCC densities of 1.9 to 2.5 g/cm³. Statistical analyses show thatcompressive strength, elastic modulus and density increase withincreased filler and fiber reinforcement content.

Tensile Strength

ASTM C 496-96 Standard Test Method for Splitting Tensile Strength ofCylindrical Concrete Specimens [reference 9] was used as a guide to testthe tensile strength for the composite cylinder specimens. A Soiltestmachine was used to produce the compressive force.

Bearing strips were constructed from 6.4 mm thick oak plywood. Widths ofthe plywood bearing strips were 25 mm and the lengths were 114.3 mm.Supplementary bearing bar was constructed from a 12.7 mm thick aluminumbar. Aluminum bar had a width of 38 mm and the length of the bar was114.3 mm. Test specimens were constructed from different compositemixtures and had diameters of 50.8 mm and lengths of 101.6 mm. 152 mmdiameter steel spacer blocks were used as the lower bearing platform.

Loading rate was constant and within the range of 689 to 1380 kPa/min. Acenterline was drawn on one end of the cylinder specimens and thediameter of the cylinder specimens was determined by averaging threediameters along the centerline. Three diameter measurements were taken,25 mm from each end and one in the middle of the cylinder specimens.Lengths of the cylinder specimens were determined by averaging twolengths.

Cylinder specimens were positioned by centering one plywood strip on thelower bearing platform lengthwise and placing the cylinder specimenlengthwise so that the centerline was vertically over the center of thewidth of the plywood strip. Then the top plywood strip was placed overthe cylinder specimen lengthwise and centered over the centerline. Theupper bearing bar was then centered over the top plywood strip. The ramwas lowered so that it came in contacted with the upper bearing bar. Thecylinder specimen, plywood strips, and upper bearing bar were thenaligned and centered.

The testing machine was then set to controlled test, which started theloading. Loading continued until the load indicator decreasedsignificantly. This decrease indicated that the cylinder specimenfailed. Maximum load was then recorded to the nearest 0.2 kN division.The testing machine was unloaded and the sample removed. Plywood stripswere then disposed. This process continued until all of the cylinderspecimens were tested.

Results indicate that the average splitting tensile strengths for 96specimens is 4.3 MPa, which is greater than the ordinary PCC strength of1.5 to 3.5 MPa. Further, statistical analyses indicate that tensilestrength increases with increased filler content and fiber reinforcementcontent.

Durability Testing

Two durability tests were conducted to evaluate the composite mixturesunder various environmental conditions similar to which sewer pipes aresubjected—water absorption and sulfuric acid resistance. Specimens forthe water absorption and acid resistance tests were made by cuttingdiscs off of cylinder specimens.

Water absorption tests were conducted to indicate the amount of waterthe various composite mixtures absorbed. ASTM D 570-98 Standard TestMethod for Water Absorption of Plastics [reference 10] was used as aguide to test the water absorption of the composite specimens. 50.8 mmdiameter specimen discs were cut off of the cylinders using a powermiter saw with a masonry blade to a thickness of 6 mm.

One disc for each composite mixture was tested for water absorption.Discs were placed in the same container of tap water. The disc's weight,thickness, and two diameters at a right angle from each other weremeasured prior to submerging them into the water. Discs were placed intothe water so a section of one part of the circumference touched the sideof the container and another section of the same edge touched the bottomof the water container. The specimen discs were then left alone for aperiod of one week at room temperature. After one week, discs wereremoved from the water one at a time. Surfaces of the specimen discswere then dried with a cotton cloth rag. Their weights were recorded tothe nearest 0.01 g and then the discs were immediately placed back intothe water container. The water absorption test was conducted after thefirst week and every two weeks thereafter for a period of seven weeks.

Results are presented in Table 3. The Δ symbol is the percent differencein water absorption between composites with filler and pure plastic.Positive numbers indicated that the composites with filler absorbed morewater than the pure plastic. All specimens with sulfur trioxide contentshigher than 12% had high water absorption. Specimens with CFBBA, whichhas a sulfur trioxide content of 30.7%, exhibited water absorption ofapproximately 12%. The RCF material absorbed the least water.

Sulfuric acid, which can be produced from bacteria in sewage, isresponsible for destroying PCC sewer pipes. For this reason, thecomposite mixtures were tested in a 10 percent by volume sulfuric acidand water solution. ASTM D 543-95 Standard Practices for Evaluating theResistance of Plastics to Chemical Reagents [reference 11] was used as aguide for this procedure. Specimen discs weights, thicknesses at thecenter, and two diameters at right angles to each other were measuredprior to introducing them into the acid. Dimensions were measured to atleast 0.025 mm and the weights were measured to the nearest 0.01 grams.

Sulfuric acid was placed into Mason canning jars and the discs were thensubmerged into the acid. Each disc was placed in a separate jar. Afterplacing the discs into jars, the lids were screwed on and the jars wereleft alone at room temperature for a period of one week. After one week,the lids of the jars were removed and specimens were taken out of thejar using tongs. Specimens were rinsed under running tap water to removethe sulfuric acid. Then, the surfaces of the specimen were wiped dryusing a cotton cloth rag. The weight, thickness, and diameters of thespecimen were then recorded. The specimen was placed back into the jarand the lid screwed down. Observations were recorded on the appearanceof the specimen. These procedures were followed again at two weekintervals for a period of seven weeks.

Summary of the results for the acid resistance tests are provided inTable 4. The positive numbers indicate specimens absorbed sulfuric acidsolution. The RCF and pure PET plastic specimens showed the greatestresistance to a solution of 10% sulfuric acid in these acceleratedlaboratory tests.

Microstructure Analysis

FIGS. 2A, 2B, and 2C show a sheared surface for the composite mixtureincluding RCF (rock quarry crusher fines) filler particles and indicatesthat the filler particles are uniformity dispersed in the mixture andthat the fiber reinforcement is breaking rather than pulling outindicating that the fiber tensile strength is fully mobilized andtightly bound to the matrix.

Plunger-Cast Pipe Manufacturing Method and Apparatus

Polymer mortar composite pipe specimens were manufactured from theaforementioned composite material mixtures for purposes of illustrationand not limitation. Equipment used to produce the pipe specimensincluded: a hydraulic ram R, plunger piston 22, inner collapsible mold14 having an overlapping region R at a longitudinal slit, outer mold 12held on a base plate 10 by two bolts 11 securing outer mold flanges 12 fon the base plate, and concrete or steel spacers BL to rest the baseplate 10 on during cooling. The inner mold 14 has an outer diametersmaller than that of the outer mold 12 so as to define an annular spacetherebetween when the inner mold is inserted in the outer mold asdescribed below. About 18,000 grams of material was used to produce onepipe specimen with dimensions of: wall thickness 38 mm; length 260 mm;outside diameter 306 mm.

Before the pipe is to be manufactured, the filler material and molds arepreheated. The desired amount of filler is weighed out then placed intoan oven (not shown) at approximately 270° C. Preheating the waste fillershortens the mixing time and decreases the moisture content. Theplunger-cast base or bottom plate 10, outer cylinder mold 12, and innercylinder collapsible mold 14 (see FIG. 3A-3F, FIG. 4A-4E, and FIG.5A-5B) can be sprayed with a release agent, such as silicone spray, toensure the pipe separates easily from the molds. The outer mold on thebase plate and the inner mold are also preheated in the oven at 270° C.

Similar to the process for preparing composite material specimens forthe aforementioned engineering property testing, post-consumer, wastePET is weighed to the desired amount then introduced into an electricmelting pot (not shown). For the lab-scale testing described herein notall of the PET would fit into the electric melting pot for most of themixes, so PET was added occasionally as it melted. The melted PET wasmixed by hand using a metal stirring rod.

Pre-heated waste filler material is added to the melting PET. Afterplacing waste filler material into the electric melting pot, thecomposite is stirred a few minutes and left to melt. The mixture isstirred every 15 to 30 minutes to increase melting and compositeuniformity.

Once the composite has a uniform consistency, the desired amount offiber reinforcement is incrementally added to the mixture. The additionof fibers increases viscosity and requires increased mixing effort.

To prepare the plunger-cast manufacturing system, the plunger piston 22is attached to the hydraulic ram and centered as shown in FIG. 6. Oncethe composite mixture is ready, the inner collapsible cylinder mold 14is taken out of the oven and attached at the top end to the plungerpiston 22 with a hose clamp 24, FIG. 7. The bottom end of the inner mold14 is held in place by hoop stresses that result from the plunger pistondiameter being slightly larger than the inside diameter of the innermold. The overlapping region R of the slit of the inner cylinder mold 14is placed at the back of the piston 22.

After the inner cylinder mold 14 and the piston 22 are positioned, theouter cylinder mold 12 and base plate 10 are removed from the oven. Themelted composite mixture is transferred into the outer mold 12 and baseplate 10 by directly pouring from the melting pot into the outer mold onthe base plate that are centered in position in the load frame forinsertion of the inner mold 14 and plunger piston 22. About one third toone half of the outer mold is filled prior to inserting the plungerpiston and inner mold. The plunger piston 22, with a special shapedbeveled end 22 a to force material outward, and inner mold 14 on thepiston is then lowered slightly on hydraulic ram 30 and centered.

Once centered, the plunger piston and inner mold are lowered into thecomposite material with the hydraulic ram 30. As the plunger pistoncomes into contact with the composite material, the piston presses thecomposite material M outward between the inner and outer cylinder molds12, 14. The pipe thickness is then equal to the distance between themolds 12, 14, in this example approximately 38 mm. Once the piston comesin contact with the base plate 10, the hose clamp 24 is loosened todetach the inner cylinder mold 14 from the piston 22. The plunger piston22 is withdrawn and removed from the hydraulic ram 30, leaving the innercylinder mold 14 in place as shown in FIG. 8.

The final step of the plunger-cast manufacturing process is the coolingof the composite material. The molds 12, 14 on base plate 10 are placedon concrete or steel spacer blocks BL beneath the base plate 10 topromote uniform cooling. The inner cylinder mold diameter is reduced bytightening hose clamp 24 periodically. This is done to reducedevelopment of residual stresses from thermodynamic shrinkage within thecomposite material. The pipe P formed by the composite material M andmolds are allowed to cool at room temperature for about 30 minutes oruntil the composite material solidifies. The pipe P, FIG. 9, is thenextracted from the outer and inner molds 12, 14 by further tighteningthe hose clamp 24 until the inner mold 14 is loose enough to slide outby hand and unbolting the outer mold 12 to allow it to be lifted off.The pipe P is then allowed to completely cool at room temperature. Theabove method and apparatus can be used to make a tubular body using aflowable material other than the composite material described in detailabove.

Pipe Three-Point Load Test Results

ASTM C 497-98 Standard Test Method for Concrete Pipe, Manhole Sections,or Tile [reference 12] was used as a guide to test the tensile strengthfor the composite pipe specimens, FIG. 9. An MTS machine was used toproduce the compressive force. Three-edge-bearing method of loading wasused to test the ultimate 3-edge bearing strength of the pipe specimens.

Each pipe specimen was supported at the bottom by two parallellongitudinal bearing strips 40 and the load was applied through an upperlongitudinal bearing strip 42 as shown in FIG. 10. The bearing stripswere constructed from pinewood that was sound, free of knots, andstraight and true from end to end. Each lower bearing wooden strip 40had a cross-section of 50.8 mm, a height of 36 mm, and a length of 330mm. Inside corners were rounded to a radius of 13 mm. The lower woodenbearing strips were fastened to a rigid wooden base 41 with Elmer's woodglue. The lower wooden bearing strips 40 were spaced apart the minimumdistance of 25.4 mm. The rigid wooden base 41 was constructed from oakand is 171 mm wide, 61 mm high and 330 mm long. The upper wooden bearingstrip 42 was glued to a steel I-beam B with liquid adhesive. The steelI-beam had a width of 50.8 mm, a height of 77 mm, and a length of 330mm.

Vertical displacement during loading was determined using a directcurrent displacement transducer (DCDT) 47 as shown in FIG. 10. Acarriage device (upper wooden base) 49 made from wood was machined tohold the DCDT to enable measurements of vertical displacement. A woodenbase 43 was rounded on the bottom to fit the inner radius of the pipespecimen. A threaded steel rod 45 was screwed into the top of the woodenbase 43 to hold the DCDT. The DCDT was secured to the threaded steel rod45 using two zip ties. The top of the DCDT rested in a small hole in theupper wooden base 49. The top of the upper base was also rounded to fitthe inner diameter of the pipe specimens.

The rigid wooden base 43 was centered under the loading ram R. A pipespecimen was then placed on its side on the lower wooden bearing strips40 so that it was centered longitudinally and rested firmly. Next thesteel I-beam B was placed on top of the pipe specimen with the woodenstrip 42 touching the pipe specimen. The ram was lowered so that ittouched the steel I-beam B. The lower bearing strips 40, upper bearingstrip 42, and pipe specimen were then centered. The DCDT was then placedinto the center of the pipe specimen and centered.

After zeroing the MTS machine the pipe specimens were then loaded.Loading rate was variable, but did not exceed 30 kN/linear meterthroughout the duration of the test. Load and displacement were bothrecorded two times per second. Test was terminated after the maximumload decreased 200 pounds. Some pipe specimens were loaded, unloaded,and loaded again until failure occurred. As mentioned, FIG. 10 shows theMTS machine and the 3-edge bearing test setup.

Ultimate three-edge bearing strength results of the 26 pipe specimenstested are shown in FIGS. 11A through 11J and summarized in Table 5.

Pipe specimens with a 230 mm inside diameter and a 38 mm wall thicknesswere produced from composite materials. Loads to produce ultimatebearing strength, ranged from 21.7 to 94.7 N/m/mm where ultimate bearingstrength is the maximum applied load divided by the length of the pipe.Average ultimate bearing strength (D-load) for the 26 pipe specimens was53.2 N/m. Although no ASTM ultimate D-load specification exists forpipes with a 230 mm inside diameters, there are requirements fordiameters ranging from 200 to 250 mm. Twenty-three of the 26 pipespecimens exhibited greater ultimate bearing strength than are requiredby ASTM for the 200 and 250 mm diameter vitrified extra strength claypipes and all classes of non-reinforced concrete pipes.

Waste filler materials increase the ultimate bearing strength. The typeof filler material used also affects the ultimate bearing strength. Ananalysis of PET to filler ratio was conducted utilizing FBC, keeping allother design mix variables constant and indicate increasing PET tofiller ratio increases the ultimate bearing strength. Optimum PET tofiller ratio for FBC was 40/60. A higher PET to filler ratio at 33/67resulted in a lower ultimate bearing strength. Even higher fillercontents were attempted, but the PET was not able to completely coat thefiller material.

An analysis of the influence of fiberglass content was conductedutilizing LS as filler material. Percentage of fibers varied from 3 to 4percent (by weight of PET and waste filler), keeping all other designmix variables constant. The optimum fiberglass content is about 3.5percent for this mixture.

Ultimate bearing strength tests were also conducted to determine whetherthe PET material (Type 1, 2 or 3) would influence the strength. Resultsindicate that all forms of PET are similar in ultimate bearing strengthfor AFA mixture, with “Type 2” being the strongest. The impurities inthe unsorted, unwashed waste PET, therefore, do not adversely affect thestrength of the composite.

REFERENCES

-   [1] Basta, N., Ondrey, G., Rajagopal, R., and Kamiya, T. (1997).    “Plastics recyclers scramble for scraps.” Chemical Engineering    104(6), 43-119.-   [2] Gabriele, M. C. (1997). “PET finds growing use in non-food    containers.” Modern Plastics, 60-65.-   [3] U.S. EPA (1997). Characterization of municipal solid waste in    the United States: 1996 Update, EPA 530-R-97-015.-   [4] The 1980 United States Census.-   [5] Needs Survey Report to Congress, Office of Water, EPA    430/09-91-024, Washington, D.C.-   [6] The Aggregate Handbook. National Stone Association, Washington,    D.C.-   [7] US DOT, (1995). Fly ash facts for engineers, FHWA-SA-94-081.-   [8] American Society for Testing and Materials. “Standard Test    Methods for Compressive Strength of Cylindrical Concrete Specimens,”    ASTM C 39M-99, Annual Book of ASTM Standards, Volume 4.05,    Philadelphia, 2000: 18-22.-   [9] American Society for Testing and Materials. “Standard Test    Methods for Splitting Tensile Strength of Cylindrical Concrete    Specimens,” ASTM C 496-96, Annual Book of ASTM Standards, Volume    4.05, Philadelphia, 2000: 268-271.-   [10] American Society for Testing and Materials. “Standard Test    Methods for Water Absorption of Plastics,” ASTM D 570-98, Annual    Book of ASTM Standards, Volume 8.01, Philadelphia, 2000: 32-35.-   [11] American Society for Testing and Materials. “Standard Practices    for Evaluating the Resistance of Plastics to Chemical Reagents,”    ASTM D 543-95, Annual Book of ASTM Standards, Volume 8.01,    Philadelphia, 2000: 25-31.-   [12] American Society for Testing and Materials. “Standard Test    Methods for Concrete Pipe, Manhole Sections, or Tile [Metric],” ASTM    C 497M-98, Annual Book of ASTM Standards, Volume 4.05, Philadelphia,    2000: 317-325.

TABLE 1 Chemical analyses and Physical Properties of Waste FillerMaterial Property CFBFA CFBBA SFA SBA AFA PFA FBC LS RCF (a) ChemicalComposition Silicon Dioxide (SiO₂) 27.80 7.50 25.80 50.70 35.05 36.9714.91 0.25 —* Aluminum Oxide (Al₂O₃) 12.70 3.00 12.20 23.90 16.62 19.958.21 0.12 — Ferric Oxide (Fe₂O₃) 9.00 1.48 10.70 8.60 6.33 5.86 4.060.30 — Sulfur Trioxide (SO₃) 12.50 30.70 0.51 0.44 2.89 2.00 29.23 0.07— Calcium Oxide (CaO) 24.30 52.60 1.30 3.01 26.65 22.83 37.97 54.77 —Magnesium Oxide (MgO) 0.58 0.33 0.65 0.91 5.67 4.28 0.64 1.27 —Phosphorous Pentoxide (P₂O₅) 0.30 0.07 1.14 0.14 2.26 1.65 0.39 — —Potassium Oxide (K₂O) 1.36 0.29 2.64 2.53 0.37 0.53 0.69 — — SoduimOxide (Na₂O) 0.12 0.06 0.50 0.29 1.19 1.38 0.07 — — Titanium Oxide(TiO₂) 0.63 0.19 0.86 1.24 1.60 1.56 0.47 — — Strontium Oxide (SrO) 0.040.03 0.04 0.05 0.32 0.40 0.04 0.07 — Barium Oxide (BaO) 0.02 0.00 0.010.01 0.76 0.78 — — — LOI (Loss On Ignition) 10.40 3.60 42.40 7.99 0.291.80 2.9 43.00 — Total 99.75 87.87 98.75 99.81 100.00 100.00 99.81100.00 — (b) Physical properties Specific Gravity 3.06 3.04 2.43 2.422.96 2.68 2.79 2.62 2.66 Percent smaller than: 4.750 mm 100 99 100 100100 100 100 100 100 2.000 mm 100 92 100 99 100 100 100 100 100 0.425 mm100 82 98 69 99 99 99 98 100 0.075 mm 89 1 93 28 96 93 62 95 74 *Note:Data not available

TABLE 2 Composite Material Mixtures and Engineering Properties Plasticto Average Average Average Filler Ratio Percent Length of Average**Compressive Tensile Elastic (based on Fiberglass Fiberglass DensityStrength Strength Modulus Filler Type dry weight) (weight %) (mm)(g/cm³) (MPa) (Mpa) (MPa) AFA 50/50 3 13 1.58 31.6 2.06 3247 FBC 50/50 313 1.63 54.1 5.48 4108 PFA 50/50 0 — 1.66 28.3 1.78 3196 PFA 50/50 3 131.65 35.0 2.82 3394 PFA 45/55 3 13 1.69 42.5 4.00 3286 PFA 40/60 3 131.76 45.0 4.34 4043 PFA 35/65 3 13 1.83 65.4 6.83 5656 PFA 50/50 1 131.66 38.0 2.29 3216 PFA 50/50 2 13 1.67 50.1 2.97 4250 PFA 50/50 4 131.65 55.2 3.10 4605 CFBFA 50/50 3 13 1.65 58.8 8.60 5070 SBA 50/50 3 131.57 42.1 4.00 4102 PFA 50/50 3 6 1.67 38.1 3.23 2968 PFA 50/50 4 6 1.6634.1 2.53 2337 PFA 50/50 5 6 1.65 37.9 3.12 2730 PFA 50/50 6 6 1.66 35.53.98 3504 —* 100/0  3 13 1.21 23.0 2.82 1612 LS 50/50 3 13 1.33 11.62.00 1264 CFBBA 50/50 3 13 1.60 23.4 7.93 1790 CFBBA 50/50 3 13 1.6426.4 7.95 1334 CFBBA 50/50 3 13 1.66 30.7 6.61 2556 RCF 50/50 3 13 1.6349.6 6.99 4364 *Note: Indicates not required. **Note: Indicates averageof four samples each for density, compressive strength, tensile strengthand two samples for elastic modulus.

TABLE 3 Water absorption results PET to Type of Fibers Water Filler PETReinforcement Absorbed Δ Filler Type Ratio Processing (%) (%) (%) PFA50/50 1 3 4.62 0.17 FBC 50/50 1 3 8.58 4.13 AFA 50/50 1 3 4.48 0.03 AFA45/55 1 3 4.04 −0.42 AFA 40/60 1 3 3.99 −0.46 AFA 35/65 1 3 5.76 1.30AFA 50/50 1 1 3.79 −0.66 AFA 50/50 1 2 4.40 −0.05 AFA 50/50 1 3 5.050.60 CFBFA 50/50 1 3 10.65 6.20 SBA 50/50 1 3 5.26 0.81 AFA 50/50 1 33.74 −0.71 AFA 50/50 1 4 3.56 −0.89 ewdrfAFA 50/50 1 5 3.90 −0.55 AFA50/50 1 6 4.09 −0.36 AFA 50/50 2 3 4.68 0.22 AFA 50/50 3 3 4.07 −0.38Plastic PET 100/0  1 3 4.45 0.00 LS 50/50 1 3 7.17 2.72 CFBBA 50/50 1 311.76 7.31 CFBBA 50/50 1 3 12.19 7.73 CFBBA 50/50 1 3 12.36 7.91 RCF50/50 1 3 1.80 −2.66

TABLE 4 Summary of sulfuric acid test results Filler Weight ThicknessDiameter Diameter Type* (g) (mm) 1 (mm) 2 (mm) Comments PFA Specimen wasdestroyed during the fifth week of testing FBA Specimen was destroyedduring the third week of testing PFA 0.73 0.03 0.94 0.64 sides startingto crack AFA Specimen was destroyed during the fifth week of testing AFASpecimen was destroyed during the third week of testing AFA Specimen wasdestroyed during the fifth week of testing AFA Specimen was destroyedduring the fifth week of testing AFA Specimen was destroyed during thefifth week of testing AFA 0.04 0.76 1.91 2.36 pieces fell off whiledrying AFA Specimen was destroyed during the fifth week of testing CFBFASpecimen was destroyed during the fifth week of testing SBA 0.84 0.030.46 0.89 slight crack AFA Specimen was destroyed during the first weekof testing AFA Specimen was destroyed during the fifth week of testingAFA Specimen was destroyed during the fifth week of testing AFA Specimenwas destroyed during the fifth week of testing AFA Specimen wasdestroyed during the fifth week of testing AFA 2.15 0.43 1.85 2.64starting to crack Plastic- 0.20 0.05 0.36 0.48 PET LS Specimen wasdestroyed during the fifth week of testing CFBBA Specimen was destroyedduring the first week of testing CFBBA Specimen was destroyed during thefirst week of testing CFBBA Specimen was destroyed during the first weekof testing RCF 0.23 −0.18 0.15 0.36 looks the best *Note: Mix designinformation is provided in Table 3.

TABLE 5 Pipe specimen mixture and ultimate three-edge bearing strengthsUltimate Three- Strain, ε_(d) Plastic to Edge (ΔD/D) at Unload- FillerRatio Percent Bearing Ultimate Initial Reload (based on FiberglassStrength Strength Stiffness Stiffness Filler Type dry weight) (weight %)(kN/m) (%) (kN/m/ε_(d)) (kN/m/ε_(d)) PFA 50/50 3 66.9 1.6 12090 5260 PFA50/50 3 44.7 1.7 13120 12500  PFA 50/50 3 52.8 2.5 12580 —* FBC 50/50 356.2 1.0 10540 — FBC 50/50 3 54.9 1.4 12010 4080 FBC 50/50 3 68.3 1.611940 — FBC 40/60 3 94.7 1.2 23420 — FBC 33/67 3 77.8 0.6 29950 — LS50/50 3 42.9 2.1 7240 2350 LS 50/50 3.5 67.2 1.9 10540 4010 LS 50/50 450.5 2.4 9020 — LS 50/50 4 55.1 2.4 7840 7720 PFA 50/50 3 54.0 1.3 9730— PFA 50/50 3 51.4 2.9 11030 — PFA 50/50 4 50.2 1.1 13140 2940 RCF 50/505 41.3 1.2 12500 — CFBFA 50/50 6 51.3 0.6 19170 — CFBBA 50/50 3 76.8 1.511490 — CFBBA 50/50 3 50.8 1.5 8940 — CFBBA 50/50 3 49.7 1.6 10700 — SFA50/50 3 25.1 1.4 5570 1330 SBA 50/50 3 39.5 0.7 9410 3330 Plastic PET100/0  3 21.7 1.2 3680 — *Note: Indicates reload test not performed

Although the invention has been described above with respect to certainembodiments, those skilled in the art will appreciate that the inventionis not limited to these embodiment and that changes, modifications andthe like can be made within the scope of the invention as set forth inthe following claims.

1. A method of making a tubular pipe body, comprising introducing aflowable material in an outer mold, disposing an inner collapsible moldon a plunger piston, said inner collapsible mold having a smallertransverse dimension than the outer mold, relatively moving the innercollapsible mold on the plunger piston and the outer mold with thematerial therein to cause the material to flow into a space between theouter mold and the inner mold such that it can form a tubular pipe bodyin said space between the outer mold and the inner collapsible mold,removing the plunger piston to leave the inner collapsible mold inplace, and forming the tubular pipe body from the material in saidspace.
 2. The method of claim 1 wherein the flowable material comprisesa melted composite material comprising melted waste, chemicallyunmodified PET material; one or more waste solid filler materials, andsolid fiber reinforcement.
 3. The method of claim 1 further includingpreheating the outer mold and inner collapsible mold before the materialis introduced.
 4. The method of claim 1 including collapsing the innercollapsible mold in a manner to reduce its transverse dimension andallow its removal from the tubular pipe body.
 5. The method of claim 4including removing the outer mold and the inner collapsible mold fromthe tubular pipe body.